This invention relates generally to audio signal processing within a computer system and more particularly to stereo signal separation of the audio signals.
Computers are known to include a central processing unit, system memory, audio processing circuitry, and video processing circuitry, which are interoperably coupled to perform a plurality of applications. Such applications include, for example, word processing applications, spread sheet applications, drawing applications, database applications, computer games, multi-media programs, and audio programs. To process a particular application, the central processing unit executes programming instructions that define the application. While executing the programming instructions, the central processing unit evokes the other elements to perform a specific task. For example, assume that a multi-media application is being executed. In this example, the central processing unit evokes the video processing circuitry to render the video portions of the application on a computer display, and evokes the audio processing circuitry to render the audio portions of the application audible. In addition, the central processing unit may instruct the audio processing circuitry to digitize received audible signals and provide it to system memory.
As can be seen from this brief example, the audio processing circuitry has two functions: convert received audible signals (which are received via a microphone, CD player, or other audible input source) into digitized audio signals and to convert digitized audio signals (which are received from the central processing unit) into analog audio signals. The analog audio signals are then provided to a speaker, which renders the signals audible.
The converted analog audio signals may be monotone signals or a stereo signals. If the signals are stereo signals, a portion of the signals (e.g., the left channel) are provided to one speaker, while the remaining portions (e.g., the right channel) are provided to another speaker. While stereo signals provide for a richer sound, when the speakers are physically close to each other, the benefits of stereo are minimized. In other words, when the left and right speakers are physically close to each other, the resulting audible signal is very close to a monotone signal, thereby substantially reducing the benefits of stereo signals. In a computer system, the speakers are relatively close to each other, thus, due to the physical nature of the computer, the benefits of stereo is minimized.
Stereo separation techniques provide a greater stereo effect, which help recapture the stereo effects when the speakers are too close to each other. Such stereo techniques scale, delay, and mix the left and right channel signals to achieve the desired results and are described in U.S. Pat. Nos. 3,170,991; 3,246,081; 3,249,696; 4,355,203; 4,748,669; and 5,440,638. While each of these techniques provides stereo separation, they do so with relatively complex and expensive circuitry.
Therefore, a need exists for a relatively simple and inexpensive stereo separation circuit.